Luminescent tube system and apparatus



Jan. 7, 1947.

J. 'H. BRIDGES LUMINESCENT TUBE SYSTEM ANDAPPARA'IUS Filed Dec. 17, 1942 IN VEN TOR. JOHN H. ER/DGE W zww Patented Jan; 7, 1947 LUMINESCENT TUBE, srs'rEM AND APPARATUS John Herold Bridges, Paterson, N. 3., assignor, by mesne assignments, to National Inventions Corporation, a corporation of New Jersey Application December 17, 1942, Serial No. 4 9,365

My invention relates to electric, lighting systems and more particularly concerns a luminescent tube system of illumination and 'apparatus therefor.

An object of my invention is the provision of a safe and reliable luminescent tube lighting sysf' tem including a transformer source of electrical energy and a plurality, of gaseous electric discharge tubes, 'Which system is characterized by good distribution of current to the tubes, by

-- 3 Claims. (01. 315-231) simplicity, sturdiness, reliability and economical rompt and substantially simultaneous energization of the tubes, and which possesses a highly satisfactory power factor.

Another object of my invention is the vision of an electric lighting system including a plurality of tubes of negative resistance characteristics and an energizing transformer, which system is adapted for operating 'a maximum" length of the included 'light tubing, which achieves highly satisfactory regulation of the,

tube-energizing current, and which is capable of safe and efficient continued operation despitefailure of one or more of several included tubes.

A further object of my invention is the provision of a reactor having a magnetic core of high reluctance, which reactor is adapted for regu- 1ating current in luminescent tube lighting systems, which interposes substantially no impedance during no-load circuit conditions, and which interposes a high impedance where loaded circuit conditions exist.

Other objects will in part be obvious andin part will be pointed out hereinafter in connection with the following description taken in th light of the accompanying drawing. I v

My invention, accordingly, resides in the. sev-- eral elements, features of construction, and

functions achieved, and in the relation of "each of the same to oneor more of the others, the scope of the application of which is indicatedin the claims.

In the drawing illustrating a iment of my invention,

Figure 1 is a schematic front elevation of an illuminating system; while preferred embod- Figure 2 depicts a wiring diagram of theele i-l trical system disclosed in Figure 1.

As conducive to a clearer understanding of certain features of my invention, it may be noted at this point that gaseous electric discharge operation. Numerous different physical dispositions orarrangemen'ts of the tubes, moreover, are mad'elpossiblein obtaining desired lighting efreefs, and the use of a variety of fillings such as fluorescent salts or phosphors as active ingredients of the tubes makes pleasing color combinations possible.

Despite the extensive acceptance of gaseous discharge tube lighting systems in illumination fields, including for example, such uses as in factories, stores, and private homes, many known systems present undesirable features which are important from a commercial standpoint. Certain offthe' systems include hot cathode tubes which require preheating before initial starting is successfully achieved. In such systems the tubes flicker during thef preheating period and considerable delay occurs before steady operation is obtained, The hot cathode systems, particularly those which operate at low voltage, also are found tube lighting systems have, in recent years, comev more and more into extended use in many'varied phases of illumination. There are many'advantages which justify the" use of these new light-'1 ing. systems; among these being characteristic to give uncertain and unstable performance at low temperatures. Other known systems of lighting possess a power factor which is far from ideal and thus are ineiiicient in operation.

There, too, are systems of the plural gaseous electric discharge tube typeswhich are incapable of continued operation in the event of failure of one or more of the included tubes. This latter objection is notable especially in lighting systems comprising a plurality of series-connected tubes'which' are energized across a single pair of transformer output taps. In such systems it is necessary to replace all burned-out tubes to make system operation possible. The number, size, or lengthoftubes employed, moreover, essentiallyis sharply restricted because of the high energizing voltage required and because of operating voltage limits imposed by the Fire Underwrit-ersp In still other heretofore known multi-tube lighting systems, the tubes are connected in parallel in order to prevent the required electrical potential from reaching prohibitive values. There,is,'howe'ver, a tendency in these systems for an included of low starting potential or of high conductance to draw such a large part of the instantaneous load current available that other included tubes either fail to start, or when theydo start, draw such light currents that the currentdensities are wholly insufiicient to produce the desired brilliant glow.

L .6 of theouts'tanding objects of my inventidii, accordingly,' is the provision of a transsystem of illumination includ ing a plurality of gaseous electric discharge tubes, in which system all tubes promptly reach substantially full conductance and brilliance and give a stable quality of illumination both in and after starting, and in which a maximum length of tubing is efficiently operated without violating.

the requirements of theFire Underwriters.

In the general practice of my invention, I pro-. vide a system of illumination which includes a:- s'tep-up transformer, and a plurality of gaseous electric discharge tubes connected. in; parallel circuits across the output side of the transformer. Each tube circuit includes an inductive react: ance, a gaseous electric discharge tube-and .a-condenser connected in series. The system, I find is of particular advantage where some eight or ten or more gaseous electric discharge tubes oreven'" as few as four such tubes are employed in .indi:--. vidual parallel circuits across the transformer secondary winding. The inductive .reactances. employed preferably are of such type'as is more fully pointed out hereinafter.

As illustrative of the practice of myinvention', in Figure 1 there is shown an electric'lighting system which includes a step-up transformer III having a shell-type core comprising an inner core portion II joined on opposite sides by outer 6- shaped core portions I2 and I3. The core is made of paramagnetic material; the outer portions of the core preferably having a composite cross-sectional area approximately equal to that of the inner core portion. The shell-type core, of course, provides two main magnetic circuits, one such circuit including inner core portion I I and outer core portion I2, and the other includinginner core portion II' and outer core portion. I3. My lighting system, however, may comprise a core'-. type step-up transformer rather than the shell type illustrated. In such instance, the transformer core would provide but one main magnetic.

circuit.

A primary coil I4 wound. illustratively of. heavy gauge wire is disposed about inner core portion II. Leads I6 and I1 extendfrom terminals of this primary coil to an alternating currentservice I8 conveniently of 110 or 220 volt rating. A.

' secondary coil I5, also disposed about inner .core.

portion I I, is wound, for example, of relatively small gauge wire, and possesses such number of. turns as to have induced thereinv a. desired stepped-up output voltage. Both coils fit snugly within the confines of the outer core portions so as to provide a compact transformer unit.

While it is within the province of myinvention to employ the transformer II] as .an ordinary transformer, with the primary and secondary. windings related only inductively, I prefer toproduce the required high secondary terminal volt-. ages by means of autotransformer connection. I therefore connect adjacent terminals of primary winding I4 and secondary coil I as by means .of lead I9, placing the coils in series. Although. in the present embodiment the primary winding I4 and secondary coil I5 are disposed in. closely, adjacent relationship on the magnetic core, I find. certain advantages in superimposing thecoils one atop the other. Where the coils are superimposed, considerable saving in core .iron, for example, is enjoyed and greater compactnessv of. construction is achieved.

When electrical current flows through the primary winding I4 from source I8, as after closure of a suitably disposed switch (notshown), a magnetic flux isv developed inthetransformerv core... In way of illustration, assume a inomentaryflow 4 of current through primary winding I4 from left to; right in Figure 1 of the drawing. A magnetic flux is induced which courses from the primary winding to the right along inner core portion IIQ-linking secondary coil I5 and returning to the left along, outer core portions I2 and I3 to the primary winding. A high voltage, accordingly, is induced in the transformer secondary, which winding, with autotransformer connection, consists of windings I4 and I5 connected in series.

During thenext subsequent half cycle of current, when the direction of current flow through 7 primary. winding I4 is reversed, flux courses I siblegtodeliver current ,through-theentire system without creating a leading power factor.

through inner cor portion II to the left in Fig- The flux, in returning to the primary winding, courses along outer core portions I2 and I3'to the right, and back through inner core portion, II to-the left. The transformer secondary coil I5 is interlinked by the returning flux and a secondary electromotive force of high value once more is induced in the transformer secondary winding.

In'the illustrative embodiment shown in Figure 1, I employ four or more fluorescent gas discharge tubes, such as TI, T2, T3, T4, connected in respective .parallel circuits across the autotransformer windings of transformer III. The circuit I provided for tube TI conveniently is traced from the righthandside of secondary coil I5 over lead 2I' tolterrninal' '23; thence over leads 24 and 25, through winding WI of reactor RI; over lead 33 through condenser CI and leads 3'! and M to terminal'22; thence over lead I6 and across primary winding I4; over lead, I9 and through secondary coil I5 back to the point of beginning.

Another tube circuit, that is for tube T2, conveniently is traced from the righthand side of secondarycoil I5 across lead 2 I, terminal 23, and leads 2 4 and 26, respectively; through winding W2 of reactor R2 and over lead 30; through tube T2,. lead 34 and condenser C2; over leads 38 and 4| to terminal 22; and thence through lead I6, primary winding I4, lead I9 and secondary coil I5 back to the point of beginning.

Similarly, a third parallel circuit conveniently is traced from the righthand side of secondary coil I5 over lead 2| terminal 23 and leads 24 and 21; through coil W3 of reactor R3, lead 3| and tube T3; across lead 35, condenser C3 and leads 39 and M to terminal '22; and thence through lead I6, primary winding I4, lead I9 and secondary coil I5 back to the point of beginning.

A'fourth parallel circuit likewise is traced from secondary coil I5 over lead I5 to terminal 30; thence across leads 24 and 28 through winding ,W4 of reactor R4; over lead 32 and through tube T4, along lead 36, through condenser C4,.and through leads 40, M respectively to terminal 22; andfibackto the point of beginning through'lead I6, primary winding I4, lead I9, and secondary coil I5.

It will be understood that still other tube load circuits, similar to those .just described, preferably are provided by connecting an additional number of series-connected reactor-tube-condenser units in parallel across the transformer secondary winding. In the embodiment shown in Figure 1, leads 24 and 4| conveniently are extended to the right and additional reactor-tubecondenser units are connected in spaced relationship across the extended leads.

Through the combined use of av condenser. and a reactorv in each parallel tube circuit, it is Dosthough each condenser gives a leading current, the corresponding reactor oifsets this with a lagging current. In other words, the reactors in conjunction with the condensers create a system power factor of substantial unity. There is, moreover, no marked tendency in the several tube circuits for one circuit to draw such high currents that the current density in a remaining circuit is insufficient to produce light at full brilliance.

My lighting system is highly efficient in operation and has particular utility where some eight or ten or more gaseous electric discharge tubes, or even as few as four of such tubes of substantial length, are to be energized. -With an. increased number of tubes in the system, installation costs are readily justified when compared with the cost of heretofore known equipment required for energizing a like number of tubes. Where more tubes are employed, core losses suffered in the system decrease, and operational efliciency increases all the more.

The tubes employed are found to have long life at least partially due to the excellent control over energizing current maintained in the system. The current controlling and distributing action achieved as between the several parallel circuits is safe and reliable. Should either a reactor or a condenser in a given parallelcircuit become short-circuited, the other alone would serve to maintain current flow in that branch within safe limits.

suppressed during initial starting of the tubes.

It has, accordingly, been advantageous to evolve for use in my system an improved reactor which displays little, if any, current. controlling action when ho-load'conditions prevail, but which instantly interposes high reactance when the tube load is energized and high currents begin to flow.

A reactor, illustrative of the type just mentioned, is indicated generally in Figure 1 by the reference character RI. The embodiment shown includes a shell-type core comprising a longitudinal inner core portion 22, having a reactor winding WI mounted thereon and terminating at one end in oppositely extending transverse portions El, E2. Outer core portions 2|, 23 extend from the other end of inner core portion 22, enclosing the winding WI on opposite sides of the inner core portion, and terminating just short of portions El, E2, thus forming therewith air-gaps GI, G2 of calibrated high reluctance. legs 2|, 23 of like cross-sectional area and to maintain a symmetrical disposition of all component core legs. It will, however, be under-stood that the symmetrical construction is not absolutely essential.

Similarly, reactors R2, R3, and R4 comprise inner core portions 22a, 22b, and 220, respectively, having corresponding laterally extending end portions E3, E4; E5, E6 and E1, E8. Outer leg portions 2 la, 23a; Ht, 231); 2Ic, 23c; extending from opposite sides of the lefthand ends of the inner core portions, form air-gaps G3, G4; G5, G6; G1, GB of calibrated reluctance with the laterally extending end portions. In the present embodiment the reactors RI, R2, R3 and R4 are designed for the same or similar tube loads, and are substantially alike in construction. It will, however, be understood that the reactors, as well I prefer to make 6 as the condensers CI, C2, C3 and C4, may possess different current limiting qualities depending, for example, upon the tube loads to be energized in the individual parallel circuits. The reactors, moreover, may to good advantage be of the core type having a single magnetic circuit and one included air-gap of calibrated reluctance.

When the primary circuit of transformer I 0, including source I3, lead I6, primary winding I4 and lead I1, is closed by means of a suitable switch (not shown) an induced voltage is impressed across output terminals 22, 23. This voltage rises and falls at the same rate as does the current through the primary winding I4. With the change in voltage, even though no current be flowing through coils WI, W2, W3, W4 (assuming that the tubes TI, T2, T3, T4 have not yet been energized), a tendency exists to develop a flux in the magnetic paths or circuits in the reactor cores. as to induce in the coils WI, W2, W3, W4, by selfinductance, a voltage tending to oppose the main secondary voltage thereacross, and thus to decrease the total voltage across tubes TI, T2, T3,

Without the provision of the included airgaps in the reactor cores this decrease in secondary voltage could reach important values and could appreciably retard the initial striking of the arcs across the tubes. It is to nullify the effect of the self-induced voltage that the included air-gaps GI -G8 are provided.

Before any tube is energized, the only current flowing through the secondary circuit is that small quantity due to the condensive action of the tubes themselves, and to the power-factor-correcting condensers CI, C2, C3, C4. Assuming now, with respect to Figure 1, a momentary halfcycle of current flow through the coils Wl, W2; W3, W4 (prior to the striking of tubes TI, T2, T3,

T4), flux courses in the reactor core of coil W to the left along central leg 22 and then branches off in separate directions along legs 2 I, 23 to airgaps GI, G2 respectively. Because of the small quantity of current flowing in coil WI, and became of the high reluctance of air-gaps GI, G2,

little, if any, of the fiux crosses these air-gaps and returns to leg 22 over reactorcore portions E I, E2.

At the same time, flux produced by the small current flowing through coils W2, W3, W4 courses to the left in Figure 1 along legs 22a, 22b, 22c and, dividing, courses over corresponding outer legs Zla, 23a; 2lb, 23b; 2lc, 230; to air-gaps G3, G4; G5, G3; and G1, G8. The small magnetomctive force set up by windings W2, W3, W4, and the high reluctance of air-gaps G3GB combine in preventing the passage of more than a very small quantity of flux at the most to end core portions E3-E8 and back to windings W2, W3, W4. During the next half-cycle of current flow, of course, the direction in which the flux tends to course over the cores of reactors RI, R2, R3 and R4 is just the reverse of that discussed. To illustrate, the flux tends to course through the core of re actor RI to the right along central leg 22 and over laterally-extending portions El, E2 to airgaps GI, G2. Similarly, in reactors R2, R3, and R4, fiux tends to course from windings W2, W3, W4 to the right along inner legs 22a, 22b, 22c, respectively, and over laterally-extending core portions E3E8 to air-gaps G3G8.

Because of the small amount of flux coursing these high reluctance reactor circuits while the tubes TI, T2, T3 and T4 are not energized, there is little self-inductance in the coils WI, W2, W3, W4 and consequently but little, if any, weakening The direction of this flux is such.

of the main secondary terminal voltage. The full value of the-secondary voltage remains substantially unimpaired, and is impressed directly across the tube loads. The tubes are energized readily and loaded conditions then prevail in the secondary circuits. A high current tends to flow in the system throughout the time that the tubes remain energized.

As soon as this high current flow is established in reactor coils WI, W2, W3, W4, however, the conditions in the magnetic circuits of corresponding reactor cores undergo material change. A high :flux now isset up in the magnetic circuits traced hereinbefore, this flux passing across'airgaps GI-GB in considerable quantity. A voltage then is induced'in coils WI, W2, W3, W4, which is proportionate to the increased current and which opposes a further increase of current through the coils. In other words, the induced voltage tends to resist change in thecurrent.

It will, therefore, be seen that the reactors not only permit substantially full terminal voltage to be impressed across the corresponding tube loads at the time of starting, but serve to counteract the tendency for increase in current flow due to decrease in resistance of the tube loads or due to short-circuiting. The air-gaps in the reactor magnetic circuits, being of such calibrated reluctance as to prevent a substantial amount of no-load flux from passing thereacross and yet not being of such high reluctance as to prevent an appreciable amount of flux from crossing while the tubes are energized, are instrumental in main- 'taining the tube-energizing current within safe and properly controlled limits without impairment of the rapid starting characteristics of my tube lighting system.

The gaseous electric discharge tubes Tl T2, T3, T4 are either hot or cold-cathode tubes. It may be well to note, however, that since hot-cathode tubes are readily available on the market, while at this stage of the art, cold-cathode tubes are obtained only on special order, I prefer to use the former. The terminals thereof preferably are shunted for cold-cathode operation. So employed, such tubes display long life without substantial impairment of their light-emissive qual-. ities. Th tubes preferably are lined with a fluorescent coating or phosphor and are gas-filled with a gas such as neon, argon, helium and. the like, with or'without a filling of mercury vapor. The tube electrodes, as well as the gas filling in the tubes, are designed to facilitate the copious production of radiations in the visible spectrum.

Because of the high energizing voltages maintained, the tubes of my lighting system strike eX- tremely rapidly and give off a steady light during operation, even under prevailing cold weather conditions. I find that in using a high secondary terminal voltage of, for example, 550 volts, which is within the limits permitted by the Fire Underwriters for autotransformer equipment, a maxi mum length of tubing is successfully energized. The combined use of a condenser and a reactor in each of the parallel tube circuits gives good distribution of current among the several circuits as well as proper control of current during the periods of energizationof the tubes. The particular parallel arrangement of tubes employed, more-'- over, gives a higher operating voltage for each of the tubes than does the conventional series connection heretofore employed.

Thus it will be seen that with my invention there is provided a system of illumination in which the objects hereinbefore noted, together with many thoroughly practical advantages, are successfully achieved. It will be seen that a single transformer output source is used in supplying energizing current to a plurality of gaseous electric discharge tubes in several parallel circuits, and that the voltage in th several .parallel.

circuits is not only high but of substantially uniform value.

eral parallel circuits gives good control of current, prompt energization of the tubes and a steady character of illumination all in keeping with highly satisfactory power factor; and that the system is adapted for operating a maximum length of included tubing and capable of safe, continued operation despite the failure of one or more of the several tubes.

As many possible embodiments may be made of my invention and as many changes may be made in the embodiment hereinbefore set forth, it will be understood that all matter described herein or shown in the accompanying drawing is to be interpreted as illustrative, and not in limiting sense.

I claim: 7

1. A gaseous electric discharge tube lightin system, comprising, in combination, a source of electrical supply, and at least four gaseous electric discharge tubes connected in individual tube circuits with said source, each of said parallel tube circuits including a condenser and a reactor having a sh .l-type core with included air-gaps and with a self-inductance winding positioned on the middle leg thereof and connected in series with the condenser.

2. A gaseous electric discharge tube lighting system, comprising, in combination, a transformer source of electrical supply, and a plurality of gaseous electric discharge tubes connected across the output side of said transformer, each of the 1 ircuits of said plurality of tubes individually including a condenser and a reactor in series therewith, said reactor having a magnetic core with an included air-gap.

3. A gaseous electric discharge tube lighting apparatus comprising, in combination; a transformer including a primary coil for connection to a source of electrical supply, and a secondary coil connected in autotransformer relationship with said primary coil; and a plurality of parallel gaseous electric discharge tube circuits connected with said transformer secondary coil, each of said plurality of tube circuits individually including a condenser and a reactor having a shell-type mag netic core with a self-inductance winding on the middle leg thereof and with included air-gaps in th magnetic circuits of the outer legs.

JOHN H. BRIDGES.

It will further be seen that the use of individual reactors and condensers in the sev- 

